Rechargeable batteries can provide electrical power without the constraint of a power cord. They are widely used in portable devices such as cell phones, personal digital assistants (PDAs), laptops, and power tools, and now even can be used in electrical vehicles. The rechargeable batteries may be nickel-cadmium (NiCd), nickel-metal hydride (NiMH), or lithium ion (LiIon).
A plurality of battery cells can be coupled to each other in series so as to form a multi-cell battery pack. The battery pack can be recharged by a DC power source, such as an AC/DC adapter, and can be discharged through a load, such as a resistor. If the charging voltage across a battery cell exceeds a high-voltage threshold, the battery pack may be burned or even explode. If the discharging voltage across a battery cell drops below a low-voltage threshold, the battery pack may also be hazardous.